1. Field of the invention
The present invention relates to a reflectory type overhead projector which has a light source and a projecting lens provided on the same side with respect to a reflecting plate and is capable of changing the magnification of projection.
2. Description of the Prior Art
It is publicly known that there is a reflection system overhead projector which has a light source and a projecting lens provided on the same side with respect to a reflecting plate and projects a subject mounted in close contact with the reflecting plate. As overhead projectors project subjects of varied sizes, variable magnification of projection is desirable. In case of reflection system overhead projectors, however, placing a subject apart from the reflecting plate means there are two subjects on the optical path of projection and it inevitably causes the problem of producing a blurred image of the subject overlapping the proper image of the subject. Therefore, efforts are made to bring the subjects as closely as possible to the reflecting plate with the belief that a variable power overhead projector of the reflection system is hard to realize when a practically tolerable focal depth should be maintained.